Hydrolysis of Halogenoalkanes.

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Introduction

Hydrolysis of Halogenoalkanes Introduction Halogenoalkanes are compounds containing a halogen atom (fluorine, chlorine, bromine or iodine) joined to one or more carbon atoms in a chain. In my experiment only chlorine, bromine or iodine will be used. Due to the fact that the carbon - fluorine bond does not undergo Nucleophilic substitution because it is the strongest of all the carbon - halogen bond. Despite its high polarity, no nucleophile will displace it due to its high bond enthalpy. The bonds that are formed between the halogen and the carbon atom are polar, this occurs when one of the bonding atoms is more electronegative than the other and the bonding electron pair is drawn towards the more electronegative atom this causes that atom to become slightly negative and the other slightly positive. In this case the halogen becomes slightly negative (-) and the carbon slightly positive (+). Nucleophilic substitution is when the halogen is substituted by a variety of other groups. When the halogen is substituted it will become a halide ion. This means that the atom that is replacing it must possess a lone-pair of electrons. ...read more.

Middle

The initial thought is that C - I bond would be broken the slowest as the carbon is the least positively charged. However after examining the bond enthalpies of the halogenoalkanes I have come to a different conclusion, the table above show a significant decrease in bond enthalpy from C - Cl to C - I. This corroborates that the ease of which the bond is broken is more important than the than the polarity of the halogenoalkane. A nucleophile may be more attracted to the carbon atom than the halogen but unless a stronger bond can be formed between them it will not displace the halogen. So I predict that the 1-iodobutane will hydrolyse first, then the 1-bromobutane and finally the 1-chlorobutane. The Experiment Apparatus The apparatus needed for this experiment are: - * 1-Chlorobutane * 1-Bromobutane * 1-Iodobutane * Ethanol * Silver Nitrate * Nitric Acid * Sodium Hydroxide * 3 Boiling Tubes * Water Bath * Test tube rack * Thermometer * Stop Clock Method 1.) Add 1cm3 of ethanol to each test tube. ...read more.

Conclusion

* Same concentration of the chemicals used. * Same quantities of the chemicals used. Risk Assessment: Chlorobutane / Bromobutane / Iodobutane (Hazcard No. 44) * Highly Flammable * Harmful by inhalation, ingestion and skin contact * Narcotic in high concentrations * Irritating to eyes and skin * Especially dangerous with sodium, as explosive reaction may occur Silver Nitrate (Hazcard No. 87) * Causes burns * Dangerous to eyes and can blacken skin. * If ingested can cause internal damage due to adsorption of blood Sodium Hydroxide (Hazcard No. 91) * Causes severe burns * Dangerous to eyes and skin * Dangerous when reacted with small amount of water, can reach high temperature, due to exothermic reaction Actions Taken With the above chemicals, if contact with skin or eyes occurs, fully irrigate the area with water. If the solution is ingested, do not induce vomiting; drink glasses of water to irrigate the system. Safety Precautions: that must be taken when using the above chemicals are: * Where goggles at all time * Take care when pouring chemicals * Wear lab coats to avoid getting chemicals on clothes * Do not sit down when carrying out experiment * All unnecessary equipment i.e. bags and coats, put away safely. ...read more.

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